Here's a handy trick: caller inside a $SIG{__DIE__} handler will give you more useful information about where you died. Here's an example:

#!/usr/bin/perl

use warnings;
use strict;

sub call_depth
{
  my $i = 1;
  $i++ while(caller($i));
  return $i - 1;
}

sub test_sub
{
  die "Internal die";
}

sub call_sub
{
  # Override $SIG{__DIE__} to get the callstack depth where we died.
  # If another sub overrides $SIG{__DIE__}, that's OK, because 
  # it means we must have gotten to an internal sub.
  # $die_call_depth is a lexical that the $SIG{__DIE__} handler will 
  # close around, so this can be called recursively. 
  my $die_call_depth = -1;
  $SIG{__DIE__} = sub { $die_call_depth = call_depth(); die @_; };

  eval {
    no strict 'refs';
    $_[0]->();
  };
  if ($@)
  {
    # die_call_depth will be our depth + 2: one for the eval, and one
    # for the $SIG{__DIE__} sub.
    if (($die_call_depth-2) == call_depth())
    {
      warn "No such sub $_[0]: $@";
    }
    else
    {
      warn "Failure inside sub $_[0]: $@";
    }
  }
}

call_sub('test_sub');
call_sub('flerp');
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Output:

Failure inside sub test_sub: Internal die at t65 line 15.
No such sub flerp: Undefined subroutine &main::flerp called at t65 line 30.